Microinjection of the Catalytic Subunit of cAMP-dependent Protein Kinase Induces Expression of the c-fos Gene

Changes in the concentration of cAMP have been shown to regulate cell shape (Porter et al. 1974) and metabolism (Schacter et al. 1984) and have been implicated in the inhibition of cell growth (Otten et ai. 1972), although it is now believed that a sustained increase in the cellular level of cAMP constitutes a growth-promoting signal in mammalian (Rozengurt 1986) and yeast (Matsumoto et al. 1985) ceils. In Escherichia coli, the expression of genes encoding enzymes involved in sugar catabolism is activated following binding of cAMP to a catabolite gene-activator protein (cap) and subsequent binding of the complex to specific DNA sequences of cAMP-regulated genes (de Crombrugghe et al. 1984). In